Many polymeric products used today, both indoors and outdoors, as sealing or insulation material, gasket, membrane, valves or filters; as well as the polymeric products used in in vivo applications such as implants and various devices are exposed to microorganisms. These organisms adhere to the polymeric material and proliferate. Fungal development on the surface of the polymeric material can lead to fungal penetration into the material. Over time, this penetration may lead to crack formation which will limit the function of the material and in the worse case collapse of the material, FIG. 1.
This scenario would lead to that the material loses its mechanical properties and would need to be replaced. For in vivo applications this causes additional surgical procedures which are both unpleasant for the patient and expensive for the society.
Prevention of microbial adherence and proliferation on objects and surfaces has been studied and known for many years. To coat or impregnate the objects with substances that are released in a sustained manner have been known and tested for a long time. However the drawbacks are that the release is sometimes to fast and the effect vanishes. The anti-microbial effect of silver and copper for example has been known for centuries but has never been fully understood. These substances could be in form of pure metal, ions or conjugates.
Prior art presents several ways of hindering the ingrowth of fungal and other microorganisms into polymeric materials, both thermoplastics and thermosets. WO2009/045455 presents an implantable medical device comprising a thermoplastic or a thermoset treated with gentian violet (hexamethyl pararosaniline chloride). The device could contain additional anti-microbial agents such as metal salts or conjugates of for example silver, copper, bismuth, gallium and zinc.
WO2008/094876 and WO2005/014074 present polymeric medical devices, especially contact lenses, with anti-microbial properties obtained by the addition of silver nanoparticles to various polymeric materials. The anti-microbial material is obtained by forming the silver nanoparticles in situ when polymerizing the polymeric material leaving an evenly distributed silver nanoparticle device.
WO2007/017019 presents anti-microbial catheters comprising a polymer matrix and an aggregation of inorganic pigment and silver acetate. The latter combination acts as an anti-microbial agent. The inorganic pigment may further comprise one or more layers in order to obtain various optical properties.
However, some of these anti-microbial substances are controversial in respect of their toxicity to humans and animals, and their environmental harmfulness. Nanoparticles for example have been a topic of debates concerning its potential toxicity. For example silver nanoparticles have been shown to cause argyria (bluish-grey coloration of the skin) and argyrosis (discoloration of eyes). Additionally, exposure to soluble silver may cause toxic effects on to liver and kidney, irritation in the eyes, respiratorial and intestinal tract and blood cell changes. Additionally, the anti-microbial substances usually have no ability to distinguish between malign and benign bacteria and therefore kill sometimes benign and essential bacteria.